This invention relates to a high-molecular flocculant rendered water-soluble by conversion of cyano groups contained in a high-molecular material, a method for producing the flocculant, and method for efficiently processing water using the flocculant.
Description of the Related Art
In the field of processing waste water, a flocculant is used as a reagent for causing aggregation and precipitation of micro-sized particles dispersed in waste water. In the waste water, such as industrial waste water, it is a frequent occurrence that mud or high-molecular impurities are dispersed as colloidal particles. The flocculant serves for aggregating these colloidal particles for purifying the polluted water.
Of the wide variety of known flocculants, those having a molecular structure of a long chain and exhibiting high hydrophilicity are high-molecular flocculants which are used extensively because addition of only a limited amount thereof to the colloidal particles leads to significant aggregating effects. The high-molecular flocculants are classified into an anionic type, a cationic type and a nonionic type depending on static charges on dissolution in water. Since a majority of colloidal particles are charged to the positive or negative polarity, extremely large flocs are formed to lower the turbidity highly efficiently by properly selecting the high-molecular flocculants depending on the polarity of the static charges.
In the field of manufacturing industrial products, high-molecular material, containing acrylonitrile as a monomeric unit, are used extensively. Among the high-molecular materials containing acrylonitrile, there are polystyrene based resins, typified by nitrite resins, ABS (acrylonitrile-butadiene-styrene resins), SAN resins (styrene-acrylonitrile resin), AAS resins (acrylonitrile-acryl-styrene resins) and ACS resins (acrylonitrile-chlorinated polyethylene-styrene resin), acrylic fibers obtained on spinning a polymer having acrylonitrile as a main monomeric unit, and NBR (acrylonitrile-butadiene rubber, also termed nitrite rubber).
A resin molded product, containing acrylonitrile as monomeric units, is superior in stiffness, dimensional stability and workability and hence is used frequently as a cover or a casing for various usages, a casing for an electric appliance or a car or as a material for components.
The acrylic fibers are lightweight, bulky and is excellent in heat insulating properties, skin touch feeling, weatherability and resiliency, so that they are used extensively for apparel alone or as a mixture with other fibers, such as wool or cotton.
The nitrite rubber exhibits superior weatherability against oils, such as fuel oil, machine oil or a tube oil, so that it is used as a fuel hose, oil seal or a belt and in particular for car use.
The acrylonitrile containing high-molecular material, used in a wide variety of industrial products, produces a large quantity of waste materials in the course of fabrication of the industrial products or on discarding of the used-up industrial products. The waste high-molecular materials are generally disposed of by techniques such as incineration, earth filling or re-melting. The former two technique belongs to discarding, while the later technique belongs to recycling.
The above-mentioned disposal techniques for the high-molecular material suffer from specified problems.
First, the incineration is accompanied by the problem of evolution of toxic gases during combustion of the waste material. That is, highly toxic cyan gas (HCN) is evolved due to cyano groups (—C═N) contained in the acrylonitrile monomer unit and which constitutes one of side chains of the polymer. Another factor contributing to incineration difficulties is susceptibility to conversion into incombustible matter as a result of carbonization.
Re-melting is a technique of heat-melting the recovered waste material for re-molding, and represents an effective technique insofar as thermoplastic resins are concerned. However, the material tends to be deteriorated in quality due to lowering in the molecular weight or oxidation, while being liable to mixing of foreign matter, such as dust and dirt. If waste materials of different originating points are processed collectively, technical and cost problems are raised, such as the necessity of re-coloring due to coexistence of various coloring agents.
Thus, discarding by land filling is nowadays thought to be most proper measures. However, selection and procurement of the proper site for a processing plant is becoming difficult from year to year, while the problem of environmental pollution cannot be evaded without difficulties.